Thermostatic variable viscosity compensator for liquid fuel conveying means



May 4. 1954 Filed July 20. 1950 D. L. RAYMOND ET AL THERMOSTATIC. VARIABLE VISCOSITY COMPENSATOR FOR LIQUID FUEL CONVEYING MEA 5 Sheets-Sheet l INVENTORS DAV/D L. BA YMO/VD Y R/(HARD J: BROWN May 4. 1954 D. L. RAYMOND ET AL 2,677,501 I THERMOSTATIC, VARIABLE VISCOSITY COMPENSATOR FOR LIQUID FUEL CONVEYING MEANS Filed July 20, 1950 s Sheets-Sheet 2 & FIG. 8.

INVENTORS IHI 0 DAV/D L. RAYMOND BYE/fH/IPD \Z'BROyV/V 3 Sheets-Sheet 3 VARIABLE VISCOSITY COMPENSATOR May 4. 1954 D. RAYMOND ETAL THERMOSTATIC.

FOR LIQUID FUEL CONVEYING MEANS Filed July 20, 1950 Patented May 4, 1954 UNITE D STATE TEN T OF F ICE tion Steve Comp ration of Ohio lapplicat'ionlllilyigl), 1950, Serial No. 174,808

4 Claims. l

Our invention has reference, in a general way, to heating apparatus of the class incorporating a liquid fuel burner, and that is employed on automotive vehicles for warming the engine to facilitate starting in ccld weather and/ or for heating the-interior of aveh-icle for the'protection of' its-contentscr the comfort of its occupa'nts, the invention being concerned more particularly with automatic means for effecting a-substantially uniform rate of flow of fuel to the burner regardless'of "changes in ambient temperature to which the fuel 'is subjected and by reason of which its viscosity varies.

Vehicles of the sort on which such heating apparatus is usually employed are required to opcrate throughout an ambient temperature range from above freezing to well below zero, sometimes as low, for example, as minus 70 F. Prior to our invention, the rate-of flow of fuel supplied to the burner of the engine heating apparatus was ordinarily set at a given amount per unit of time by providing a metering device characterized by a capillary'restriction of a capacity to accomplish a maximum fuel supply to the burner consonant with safe operation in the upper ambient temp'era turerange. However, it was found that when the temperature dropped below, roughly, the viscosity of the liquid fuel increased to such an-extent-th-at the how rate-Which, other things being constant, is dependent upon the viscositywas so decreased that it became difficult to igni te the fuel, or to maintain sufficient combustion to -eilec't proper heating of the vehicle parts, partic-ularl-y the vital parts of the engine. By way of example: where the fuel delivery rate to the burner set for 12 cubic centimeters per minute, at an ambient temperature of approximately 40 above zero upon a decrease in the ambient temperature to below zero F., the fuel delivery rate might decrease'to that of three to five cubic centimeters per minute. In addition to the decrease in flow due to the increased viscosity of the fuel, there'has been encountered an additional difficulty resulting from particles of ice, partially congealed fuel and foreign matter clogging the capillary passage of the metering device.

The primary object of our invention is to provide means that operates automatically to overcome the wide variation in the rate of fuel flow to the burner of the engine heating apparatus heretofore caused by fluctuations in the ambient temperature to which the heating apparatus is subjected in operation.

Another object is to provide means of the above 2 mentioned character which operates in such manneras to prevent clogging of the fuel passage by ice particles, clots of congealed fuel and for eign matter that may, under certain conditions, be present in the fuel.

A further object is to provide a unitary structure incorporating a metering device and a thermosensitive element for actuating the same that will maintain a constant predetermined flow of fuel to the burner of the heating apparatus throughout a very wide range of ambient temperatures. V

A still further object is to provide an adjustment between the metering device and thermosensitive element by virtue of which the mean flow resistance of said device may be varied ac cording to the requirements of different kinds of liquid fuels.

More specifically, "it is an object of the invention to provide a flow control device or variable viscosity compensator comprising two relatively movable elements defining between them acapillary viscous flow passage, the flow resistance of which is altered by 're'alative adjustment of said elements, and thermosensitive means, so arranged as to be subjected to the temperature affecting the viscosity of the liquid fuel being handled, for relatively adjusting said elements to respectively increase and decrease the flow resistance of said passage in response to arise and fall of said temperature.

A further object is to so relate the thermosen'sitive means to the fuel inlet of the device or compensator that the fuel will act upon said means, by impingement or otherwise, to vibrate the means and accordingly impart relative vi bration to the aforesaid elements which will tend to-dislodge from the capillary viscous flow passage any material tending to clog it.

Another object of the invention is to provide, in conjunction or association with a flow control device of the above character, a safety valve that is closed and held closed by the action of the thermosensitive means when the ambient temperature is above a predetermined value or, in,

other words, above'the temperature range within which the device is designed or adjusted to operate as a variable viscosity compensator.

A still further and more general object of our invention is to provide a sturdy and durable and relatively simple construction that is readily fab ricated, easily adjusted and serviced, and that is not liable to get out of adjustment when in service.

The foregoing objects, With others hereinafter appearing, are attained in the embodiments of the invention illustrated in the accompanying drawings, wherein like reference characters designate like parts throughout the several views.

In the drawings, Fig. 1 is a perspective view of one form of our invention; Fig. 2 is a central vertical section through the same; Fig. 3 is a transverse section on the line 3-3 of Fig. 2; Fig. 4 is a perspective view of the bimetal strip that constitutes the thermosensitive element of the constructions illustrated in Figs. 1 to 8; Fig. 5 is a side elevational View, partly in section, of the metering sleeve appearing in Fig. 2; Fig. 6 is an elevational view of the metering pin employed in conjunction with said metering sleeve; Fig. '7 is a view, similar to Fig. 2, of a modification; Fig. 8 is a side elevation, partly in section, of the metering sleeve employed in said modification; and Fig. 9 shows the flow control device or variable viscosity compensator combined with a fuel impeller or pump, in the liquid fuel conveying means between a fuel tank and a burner of a heating apparatus.

The flow control device or variable viscosity compensator illustrated in Figs. 1 to 6, comprises a body member designated, generally, by the reference numeral i, and a casing 2, shown as drawn from sheet metal. Said body member includes a circular part 3 of substantial thickness that is reduced at its lower end to provide a circumferential shoulder E, the plane of which is normal to the axis of the part 3, and a cylindrical portion 5 that is externally threaded for the reception by an internally threaded ring 6, suitably secured within the enlarged upper end 8 of the casing,

which end extends above the ring 6 and surrounds the part 3 of the body member. A packing gasket 9 is compressed between the ring 6 and the shoulder thereby to seal the casing 2.

An elongated boss H3 extends across and is shown as integral with the part 3 of the body member, and at one end is bored and internally threaded to provide an inlet port l2 into the outer end of which a pip fitting is adapted to be screwed. The inlet port, through a downward extension is thereof of lesser diameter, communicates with a fuel chamber 15 that is enclosed by the casing 2 and the part 3 of the body member Depending from the body member within the fuel chamber l5, adjacent one side thereof, is a boss i5. This boss and the portion of the body member thereabove contain a threaded axial bore which opens at its upper end into an outlet port ll. This port, like the inlet port I2, is counterbored and threaded for the reception of a pipe fitting. 2!! denotes an externally threaded metering sleeve that is screwed into said bore and, at its upper end, is provided with diametrically opposed grooves ii for the application of a screw driver or the like for turning the sleeve, as for the purpose of adjusting it within the boss I6. Access to the grooved end of the sleeve is had through a top opening in the boss ID that is substantially aligned with the metering sleeve and is normally closed by a screw plug 23.

The boss i6 is formed at its lower end with a lateral extension 25 from which depends a bifurcated bracket 26, and supported by and between the branches of the bracket is a pivot pin 21 on which a bell crank lever 23 is fulcrumed.

The metering sleeve 20 has a very gradually tapered bore Within which is disposed, in spaced relation to the wall of said bore, a correspondingly tapered metering pin 39, the lower end of which is slotted to receive one branch of the bell crank 23, said branch having a relatively deep notch that opens through its outer end within which a cross pin 32, that is carried by the metering pin, has a working fit. Desirably incorporated in the metering pin is a valve member (v i, shown as a flange or collar that surrounds the pin and has a tapered upper face that is arranged to engage, under conditions hereinafter to be explained, a valve seat 35 of corresponding taper. The other arm of the bell crank 28 is pivotally connected, by means of a pin 37, to one of the ends of a pair of links 3%, the opposite ends of said links being similarly connected, by a pin 39, to a clevis 49, This clevis has operative connection with the thermostatic means that renders the device automatic in operation. Said means, in the present instance, consists of an inverted U-shaped bimetal strip i' having legs of unequal length. The clevis do is secured to the end of the longer leg of the strip 45, whil the other and shorter leg of said strip is provided with a relatively deep notch (Fig. 4) that receives a screw 41 threadedly engaged with the extension 25 of the boss 56, and by the head of which screw the bimetal strip is clamped to the outer end of said extension. A look washer is shown as interposed between the head of the screw and the bimetal strip to insure against loosening of the screw.

It is apparent from the foregoing description that the metering pin 30 is held in position within the metering sleeve 29 by the bimetal strip, through the intervention of the clevis 49, the links and bell crank 26. It is equally clear that as the bimetal strip warps under the influence of changes in the temperature of oil contained within the chamber IE, it will adjust the metering pin in an axial direction within the metering sleeve. The mean relation between the metering pin and metering sleeve may be altered in various ways as by adjusting the metering sleeve within the boss IE; and/or raising and lowering the bimetal strip 45, which is accomplished by virtue of the notch 46, and/or by changing the effective length of the branch of the bell crank 28 to which the links 38 are pivotally connected, the latter being attained by providing a plurality of holes in the arm of the bell crank for the reception, by any selected one thereof, of the pin 3?. As an obvious alternative, a plurality of holes could be provided in any one of which the pivot pin 21 might be engaged. By virtue of the adjustments mentioned, not only can the devic be made to operate in the most desirable fashion with respect to a given grade or weight of liquid fuel, but it may b altered to meet the requirements of fuels of difierent grades within a reasonably wide range.

Fig. 9 shows the above described form of flow control device or compensator included in a fuel supply line L that leads from a tank T to the burner 33 of heating apparatus I-i. Obviously, either of the other two forms of the device herein disclosed could be substituted for the one shown. Intermediate the tank T and the flow control device or compensator, designated I in Fig. 9, is a fuei pump P. This is a conventional diaphragm pump, desirably of the well known Autopulse type, which is actuated by electrical means. Briefly, the diaphragm will be moved, as by means of a solenoid, for example, in a direction to expand the pumping chamber and draw in liquid, and it will be moved in the opposite direction by spring means so as to contract the chamber and expel the liquid. Such a pump is disclosed in greater detail in a copending app1ica-- tion of Allen Cleveland, Serial No. 754,652, filed June 14, 1947.

It is evident from the foregoing that when the pump is operating fuel will be fed intermittently to the flow control device and thence to the burner When the system is initially con-- ditioned for operation, the fuel chamber 25 of the flow control device or compensator is vented through a passage ll; in order to avoid any air being trapped within the fuel chamber, after which the passage :39 is closed by a screw 5%). As the fuel enters the chamber E5 in intermittent surges or pulsations, it impinges upon the upper end of the therinosensitive element or resilient bimetal strip d5 so as to cause said element or strip to vibrate, and the vibration of the element or strip is transmitted through the links 38 and bell crank lever 28 to the metering pin 3!]. This action will dislodge any material of a solid or semi-solid nature that tends to stick in the restricted space between the metering pin and sleeve, thereby to k ep clear the capillary viscous fiow passage.

When the system is idle for a considerable period of time, the liquid fuel therein will attain substantially ambient temperature. As previously pointed out, changes in the ambient temperature will affect the viscosity of the fuel. Now, by way of example, it may be assumed that, from a previous higher value, the ambient temperature dropped to around 50 to 60 degrees below zero when it is desired to light the burner B. corresponding temperature of the fuel in the chamber it will cause the biinetal strip 35 to warp and move the longer leg thereof in the direction indicated by the arrow in Fig. 2, thereby to retract the metering pin as and, by reason of the taper of the pin and the bore of the meter ing sleeve 2d, enlarge or increase the effective cross sectional area of the capillary viscous flow passage, defined by the opposed surfaces of the pin and the wall of said bore. At the same time, the length of the passage will be shortened inasmuch as the pin does not extend entirel through the bore. In other words, due to these two factors in the present case, the flow resistance of said passage will be decreased. Since the pressure created by the pump P remains constant, the same quantity of fuel will be delivered to the burner as under higher temperature conditions, notwithstanding the increased viscosity of the fuel. As the ambient, and consequently the fuel temperatures ri e, and the fuel becomes thinner, so to speak, the thermosensitive element or strip ll) will swing in the direction opposite that indicated by the arrow in Fig. 2 and will project the pin as further into the bore of the sleeve and increase the flow resistance of the passage between the pin and sleeve thereby to accomplish the same rate of flow of the fuel to the burner as prevailed under the former low temperature conditions.

Under abnormally high temperature conditions, such, for example, as would occur if fire broke out on the vehicle equipped with the heating apparatus, the thermosensitive element or bimetal strip 35 would warp sufificiently in the last mentioned direction to engage the valve 34 with the seat 35 and positively shut off flow of fuel to the burner, this valve being included, principally, as a safety measure.

The construction of the flow control device or compensator illustrated in Figs. 7 and 8 is so nearly like the construction above described that itwill be understood from the foregoing description, especially since the corresponding parts of the two constructions are designated by like reference characters, those applied to the modification shown in Figs. '7 and 3 being augmented by the exponent a.

The principal differences are in the casing i and in the metering sleeve 25 The boss Hi iscounterbored from its lower end for the major portion of its length and is threaded thereabove forthe reception of a threaded portion 2c of the metering sleeve 26 A circumferential groove 28 about the sleeve 2%, immediately below the threaded portion thereof, provides clearance for the thread cutting tool, and below said groove the sleeve is smooth excepting for a circumferential, channel 225 that contains a so-called O- ring 23 that seals the joint between the sleeveand the surrounding bore of the boss. The ca ing 2 is attached to the body member i in substantially the same manner as in the first described construction, and the joint between the two is made fluidight by a packing washer s To id in screwing the casing onto the body member, the external surface of the peripheral wall of the casing a is shown as formed with ribs 21 and in case it is desired to use a tool, such as a wrench, for-this purpose, the casing, which is desirably a casting, is formed at its lower end with axial. boss 2, which may be square, hexagonal, or of other appropriate shape on its outer side. The boss is shown as hollow, to serve as a sediment sump, and it has a threaded drain opening that is normally closed by a screw 2 The operation of this form or" the flow control device or compensator is identical with that of the first described form.

It will be apparent to those familiar with physics, that the metering means of the how control device or compensator embodies the principle of Poiseuilles law. However, said means, in order to adapt it to our purpose, involves two relatively movable elements that define, between them, a

- capillary viscous fiow passage, the flow resistance of which is altered by relative adjustment of said element.

In the embodiments above disclosed, said means comprises the tapered metering pin, and the metering sleeve which has a tapered bore wherein the pin is disposed.

The basic principle of operation of the metering means lies in causing the liquid fuel to pass through. a relatively long, restricted passage, such asv one defined between two elements, 1. e. a metering pin or restrictor, and the surrounding wall of a bore wherein said pin or restrictor is disposed. The fuel passing through a passage defined as above is subject to a viscous type flow that is governed by the formula:

Q=volume flowing per unit of time R=radius of the passage =viscosity of the fuel =Length oi the passage as bounded on the outside by the passage wall and on the inside by the restrictor pin surface.

pip2-=The difference in pressure between the inlet (for) and outlet (p2) of the passage.

Thus it will be seen that the volume of fuel flowing through the passage will increase if the inlet pressure (m) is increased or if the radius R (and consequently, the equivalent area) of the passage is increased; and the volume will decrease if the viscosity (1 of the fuel increases (as caused by lowering the temperature of the fuel) or if the effective length (L) of the passage is increased.

Our invention comprehends the provision of means for automatically and controllably varying certain of the above factors to compensate for the effect caused by changes in the viscosity factor. In our case, the length L of the peasage, and/or the equivalent area (a function of the radius R) of said passage are varied in such manner as to compensate for the uncontrollable change in viscosity due to temperature change; and the pressures 211 and 112 are maintained substantially constant. It may be explained, in passing, that, according to tests, embodiment of our invention performed satisfactorily for a number of liquids having a relatively large range of viscosity values.

Having thus described our invention, what we claim is:

1. An automatic variable viscosity compensator comprising a body member threaded at its lower end, a casing open at its upper end and internally threaded adjacent the latter end for screw connection with the body member, the casing enclosing a liquid chamber, a boss depending from the body member into said chamber adjacent one side thereof, the body member having an inlet port that opens into said chamber adjacent the opposite side of the latter and provided with an outlet port substantially opposite the inlet port, said boss and the part of the body member thereabove containing a bore that opens at its upper end into the outlet port and at its lower end into said chamber, said bore being threaded, an externally threaded metering sleeve within said bore, a bracket extending laterally and downwardly from said boss substantially central of the liquid chamber, an inverted U-shaped bimetal stri having a short leg secured to the side of said bracket opposite the boss and a long leg that depends below the horizontal plane of the corresponding end of the bracket, a bell crank lever pivoted at the angle between its branches to the lower end of the bracket and arranged with one of its branches substantially horizontal and the other substantial vertical, operative connections between the lower end of the last mentioned leg of the bimetal strip and the vertical branch of said bell crank lever, and a metering pin supported by the horizontal branch of said lever within the bore of the metering sleeve, the peripheral surface of the pin and surrounding wall of the bore of the metering sleeve being spaced apart to provide a capillary viscous flow passage therebetween.

2. An automatic variable viscosity compensator according to claim 1, wherein the body member is provided with an opening above and in substantially axial alignment with the metering sleeve, the upper end of the metering sleeve being formed to provide a tool engaging part that is accessible through said opening, and a closure for said opening.

3. An automatic variable viscosity compensator comprising a body member, a casing joined thereto and enclosing therewith a liquid fuel chamber, the body being provided with an inlet port and an outlet port, the former opening into said chamber, the body member having also a bore leading from the chamber to the outlet port, a metering sleeve in said bore and having, in-

turn, a tapered bore whose smaller end is adjacent the outlet port, a complementarily tapered metering pin disposed within the bore of the sleeve in spaced relation to the surrounding surface thereof to provide between the pin and said surface a capillary viscous flow passage, a bimetal strip supported at one of its ends by the body member within the fuel chamber, operative connections between the opposite end of said strip and the metering pin whereby, when said strip warps, in response to changes in temperature of the liquid fuel in the chamber, the pin will be adjusted axially of the sleeve to vary the flow resistance of said passage, the first mentioned bore being threaded adjacent its upper end and therebelow is enlarged in diameter and is smooth, and said metering sleeve being externally threaded adjacent its upper end for cooperation with the threaded portion of said bore and being smooth and of a diameter therebelow to be received by the smooth portion of the bore, and a packing element surrounding the lower portion of the sleeve and disposed between opposed surfaces of the sleeve and bore, one of said surfaces being circumferentially grooved to accommodate said packing element.

4. An automatic variable viscosity compensator comprising a body member threaded at its lower end, a casing open at its upper end and internally threaded adjacent the latter end for screw connection with the body member, said casing including a peripheral wall having, on its exterior, a plurality of ribs that extend substantially longitudinally of the casing, the body member being provided with an inlet port and an outlet port, the former port opening into said chamber, the body member having also a bore leading from the chamber to the outlet port, a metering sleeve in said bore, a metering pin disposed within the sleeve in spaced relation to the surrounding surface thereof to provide between the pin and said surface a capillary viscous flow passage, a bimetal strip within the fuel chamber attached at one of its ends to the body member, and operative connections between the opposite end of said strip and the metering pin whereby, when said strip warps in response to changes in temperature of the liquid in the chamber, the pin will be adjusted axially of the sleeve to vary the flow resistance of said passage.

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